The utility industry uses warning data-tags or labels in a variety of situations to instruct personnel that a potentially dangerous situation exists. For example, when a piece of equipment or a transmission line is disabled so that it can be serviced, the service person attaches a lock or warning tag to the switch while he is servicing the line or equipment, often at a remote location not visible from the switch. The workers will not accidently re-energize the equipment while the lock or tag is present.
The use of such tags is mandated not only by common sense, but in some instances government regulations require their use.
A suitable data-tag should be constructed from materials which are resistant to severe environmental conditions and non-hazardous. The design of the tag should be such that the instruction posted on it is protected from the environment, clearly visible and readable under adverse lighting conditions, and tamper-resistant, over an extended period of time. Eventually the tag may have to be removed or destroyed because the need for a warning is eliminated and a means for so doing should be provided. In many applications provisions for duplicating the information on the tag should be incorporated.
The most common type of data-tag presently being used is a vinyl tag. Vinyl has the advantages of being readily available to tag manufacturers and relatively inexpensive. However, we have found that vinyl is not strong enough in some situations. For example, when the tag is applied to switches on utility transmission lines in coastal or other high wind areas, the tag may tip and blow off the line. This type of failure may have fatal consequences. Vinyl also becomes brittle when exposed to ultra-violet rays, such as sunlight. Adding UV absorbers to vinyl is a possible solution, but vinyl with such absorbers is less commonly available and more expensive.
We have found that polyester is a better material for manufacturing warning tags. Polyester has a much higher tear resistance than vinyl. Polyester may discolor after long term exposure to the sun, but does not become as brittle as vinyl, and therefore provides a much more secure tag. Polyester has a much higher melting point than vinyl. Therefore polyester can be used in higher temperature situations where vinyl would melt or deform if it contacted or was adjacent to a hot surface. The tensile strength of polyester is as much as two to four times greater than vinyl of the same thickness. The dielectric strength of polyester is one and one-half to two times that of vinyl. While vinyl may melt or deform at temperatures as low as 150.degree. F. (60.degree. C.), polyester is usable at temperatures of 225.degree. to 300.degree. F. (107.degree. to 149.degree. C.) or higher.
Known warning tags use reinforcing grommets or eyelets in their mounting holes. Some inexpensive paper tags use reinforced paper, but grommets are far stronger and are required in environmentally severe installations. Most eyelets or grommets are made from brass, although some stainless steel grommets are used. The metal has to be ductile enough to bend easily in an eyeletting tool. Metal grommets have the disadvantage that when made of less expensive materials they can rust and even more importantly, they are conductive. When warning tags are used on high voltage transmission lines, intense electric fields are often present that may cause arcing or flashing when metal grommets are used. A non-conducting reinforcer which will increase the pull strength at the mounting hole is desirable. Plastic snap-grommets are known for use with large banners, but most are too thick to be used in utility warning tags because they could catch on equipment, are readily pried apart, hard to package, and expensive. We have developed a nylon grommet that is stronger, much thinner and harder to disassemble. The nylon grommet also can be provided with ultrasonic focusing projections for allowing the grommet parts to be welded together.
Conventionally, utility data-tags are formed from vinyl sheet about 10 mils (0.25 mm.) thick. We have found that by using polyester and increasing the base film thickness to 12-15 mils (0.3-0.375 mm.), the tags are even stronger than 10 mils (0.25 mm.) polyester. However, the tags must be removable and utility personnel prefer tags that can be removed without special tools. Since polyester is so much tougher than vinyl, it is hard to tear. We provide a stress concentrating region on the tag for starting a tear, so that the tag can be easily ripped in half. The region can be just a line cut into the tag or a shaped notch, for example V-shaped, which is more visible to the user and directs the User to the proper point at which to tear. Other methods for initiating a tear can be used, for example, slitting or scoring the surface, or providing a thinner region at the edge of the substrate.
In many applications, it is necessary to label the tag at the time it is applied. We provide a titanium dioxide coating on our polyester substrates to give the tag an exceptional pencil receptivity. By using this coating, we provide a tag that shows pencil markings in a blacker more durable form than in prior tags. Similar coatings have been used in other applications, such as credit cards, but not, as far as we are aware, on polyester utility data-tags.
The data-tag of this invention is particularly useful when embodied in a self-laminating form with or without an integral carbon paper or pressure activated carbonless record sheet. The self-laminating tag has a layer or flap of clear, preferably UV blocking film, such as polyvinyl fluoride film attached to the polyester substrate at one end. The film is covered with a layer of pressure sensitive adhesive and the unattached end is protected by a removable protective sheet. The pencil receptive titanium dioxide writing surface is formed on the front of the polyester substrate under the clear flap and normally has a printed form thereon. In use, the surface of the tag has a printed form thereon and the tag can be marked with the date on which it is installed, a signature, or the like, the protective layer pulled from the clear flap, and the adhesive backed portion of the flap pressed onto the substrate to form a durable, laminated assembly. In certain applications we also provide a carbon or pressure activated carbonless record sheet on the tag that the user can mark either separately or together with the substrate and remove from the tag to keep a record of the date and time for installation, for example. For applications in which the record sheet is behind the polyester backing the thickness of the backing is preferably from 5 to 10 mils (0.125 to 0.25 mm) thick to allow increased pressure on the record sheet. The thinner polyester base is still strong enough for all but the most severe environmental conditions.
We have found it desirable in some applications to use fluorescent and/or phosphorescent pigments for the indicia of the printed form on the polyester substrates of our tags. These pigments make the legends on the tags much easier to read in adverse conditions such as fog, rain, darkness or the like.
We provide instructions and/or illustrations on how to use the tag on the removable protective sheet that is attached to the clear flap which are visible from the front of the tag. These instructions and illustrations are therefore available to the user at the time the tag is installed, and some users find them very helpful. The instructions can be included at essentially no cost, since they are applied to a necessary component of the tag.
We provide a number of other features, some of which have been used by us and by others in the past, but never in combination with the inventive features of our new tag. For example, in some embodiments of our invention we provide a removable polyester or paper portion attached to the tag by a line of weakness, preferably a line of perforations.
While most of our tags are attached by means of a fastener threaded through the mounting hole, we provide a version of the tag with an adhesive backing that can be adhered to a flat surface.
Most tags presently in use have square or chambered corners. We have discovered that rounded corners resist delamination of the clear cover sheet more effectively, and therefore we use rounded corners on our tags.
U.S. Pat. No. 4,407,524 (Trautlein) discloses a durable data-tag having a durable backing member, an adhesive clear cover member and a plurality of identical layered, record form sheets wherein the layered form sheets are attached to the backing member at the end opposite to that which the clear cover member is attached. There is no disclosure of a polyester backing member or of a non-conducting grommet.